For a purpose of improvement in combustion efficiency and reduction in fuel consumption rate of an engine, there is developed an ignition device equipped with a high frequency wave antenna that creates a plasma generation region around a discharge electrode of an ignition plug (see Japanese Unexamined Patent Application, Publication No. 2007-113570). With this ignition device, air fuel mixture in the vicinity of the ignition plug is irradiated with a high frequency wave, thereby enabling improvement in combustion efficiency and reduction in fuel consumption rate. As an emission antenna for emitting the high frequency wave, a metal antenna is generally employed.
However, if the conventional metal antenna is used as the emission antenna of the high frequency wave, a problem is encountered that the metal antenna is insufficient in durability owing to severe wear and degradation. Furthermore, the conventional emission antenna is designed to supply the high frequency wave at a single point such as an ignition point and, therefore, is not capable of emitting the high frequency wave at an appropriate location and/or timing in accordance with flame propagation.